Methods and apparatus for enabling further L1 enhancements in LTE heterogeneous networks

ABSTRACT

A network element in a first cell in a wireless telecommunication network is provided. The network element comprises a processor configured such that the network element provides uplink and downlink grants in the first cell, wherein the first cell is a low-power cell within the coverage area of a second, high-power cell, and wherein the first cell acts as a secondary cell and the second cell acts as a primary cell in a carrier aggregation mode, and wherein at least one uplink control signal is received by one of only the first cell or both the first cell and the second cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/842,498 filed Mar. 15, 2013 by Yi Song, et al. entitled, “Methods andApparatus for Enabling Further L1 Enhancements in LTE HeterogeneousNetworks”, which claims priority to U.S. Provisional Application No.61/707,636 filed Sep. 28, 2012 by Yi Song, et al. entitled, “Method andApparatus for Enabling Further L1 Enhancements in LTE HeterogeneousNetworks”, both of which are incorporated by reference herein as ifreproduced in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to communication in heterogeneouswireless telecommunications systems.

BACKGROUND

As used herein, the term “user equipment” (alternatively “UE”) might insome cases refer to mobile devices such as mobile telephones, personaldigital assistants, handheld or laptop computers, and similar devicesthat have telecommunications capabilities. Such a UE might include adevice and its associated removable memory module, such as but notlimited to a Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. Alternatively, such a UE might include the deviceitself without such a module. In other cases, the term “UE” might referto devices that have similar capabilities but that are nottransportable, such as desktop computers, set-top boxes, or networkappliances. The term “UE” can also refer to any hardware or softwarecomponent that can terminate a communication session for a user. Also,the terms “user equipment,” “UE,” “user agent,” “UA,” “user device,” and“mobile device” might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE). For example, an LTE systemmight include an Evolved Universal Terrestrial Radio Access Network(E-UTRAN) node B (eNB), a wireless access point, or a similar componentrather than a traditional base station. Any such component will bereferred to herein as an eNB, but it should be understood that such acomponent is not necessarily an eNB. Such a component may also bereferred to herein as an access node or a network element.

Any set of cells that includes one or more cells with a smaller coveragearea than the typical coverage area of a traditional eNB may be referredto herein as a small cell deployment. A cell with the relatively largecoverage area provided by a traditional eNB may be referred to herein asa macro cell. A cell with a relatively smaller coverage area than amacro cell may be referred to herein as a small cell, a pico cell, or afemto cell. Alternatively or additionally, a macro cell may beconsidered a high-power cell, and a small cell may be considered alow-power cell. The access node in a macro cell may be referred to as amacro eNB or a macro node, and the access node in a small cell may bereferred to as a small cell eNB, a pico eNB, or a femto eNB. Whenreference is made herein to an action being taken by a cell, it shouldbe understood that the action may be taken by a component in the cell,such as an eNB.

LTE may be said to correspond to Third Generation Partnership Project(3GPP) Release 8 (Rel-8), Release 9 (Rel-9), and Release 10 (Rel-10),and possibly also to releases beyond Release 10, while LTE Advanced(LTE-A) may be said to correspond to Release 10, Release 11 (Rel-11),and possibly also to releases beyond Release 10 and Release 11. As usedherein, the terms “legacy”, “legacy UE”, and the like might refer tosignals, UEs, and/or other entities that comply with LTE Release 11and/or earlier releases but do not comply with releases later thanRelease 11. The terms “advanced”, “advanced UE”, and the like mightrefer to signals, UEs, and/or other entities that comply with LTERelease 12 and/or later releases. While the discussion herein deals withLTE systems, the concepts are equally applicable to other wirelesssystems as well.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a diagram of a UE with dual connectivity to a macro cell and apico cell, according to an embodiment of the disclosure.

FIGS. 2a, 2b, and 2c are MCS index and CQI index tables according to theprior art.

FIG. 3 is a diagram of eNB-to-eNB and UE-to-UE interference in dynamicTDD.

FIGS. 4a and 4b are deployment scenarios for low-power cells.

FIGS. 5a and 5b are MCS index and CQI index tables, according to anembodiment of the disclosure.

FIGS. 6a and 6b are MCS index and CQI index tables, according to analternative embodiment of the disclosure.

FIGS. 7a and 7b are MCS index and CQI index tables, according to anotheralternative embodiment of the disclosure.

FIG. 8 is a table of new transmission modes and DCI formats, accordingto an embodiment of the disclosure.

FIGS. 9a and 9b illustrate a new DCI format, according to an embodimentof the disclosure.

FIG. 10 is a diagram of SC-FDMA and OFDMA multiplexed in one uplinksubframe, according to an embodiment of the disclosure.

FIG. 11 is a diagram of dynamic TDD in neighboring cells, according toan embodiment of the disclosure.

FIG. 12 is a diagram of interference coordination for dynamic TDD,according to an embodiment of the disclosure.

FIG. 13 illustrates a CQI-ReportConfig information element and aMeasSubframePattern information element, according to an embodiment ofthe disclosure.

FIG. 14 illustrates a CQI-ReportConfig information element, according toan embodiment of the disclosure.

FIG. 15 is a diagram of a pico cell configured as an LTE TDD SCC,according to an embodiment of the disclosure.

FIG. 16 is a diagram of a pico cell configured as an LTE FDD SCC,according to an embodiment of the disclosure.

FIGS. 17a and 17b illustrate an RRCConnectionReconfiguration message,according to an embodiment of the disclosure.

FIG. 18 is a diagram of a downlink Layer 2 protocol, according to anembodiment of the disclosure.

FIG. 19 is a diagram of an uplink Layer 2 protocol, according to anembodiment of the disclosure.

FIG. 20 illustrates RRC signaling to notify a UE about dynamic TDD in apico cell, according to an embodiment of the disclosure.

FIG. 21 is a simplified block diagram of an exemplary network elementaccording to one embodiment.

FIG. 22 is a block diagram with an example user equipment capable ofbeing used with the systems and methods in the embodiments describedherein.

FIG. 23 illustrates a processor and related components suitable forimplementing the several embodiments of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents. Embodiments are describedherein in the context of an LTE wireless network or system, but can beadapted for other wireless networks or systems.

Embodiments of the present disclosure provide a number of techniquesthat may boost the traffic capacity in heterogeneous wirelesstelecommunication network deployments in which both larger cells andsmaller cells are present.

Traffic capacity in future wireless systems may be improved byincreasing the number of network nodes and thereby bringing the end-userdevices physically closer to the network nodes. Network densificationmay be achieved by the deployments of complementary low-power nodesunder the coverage of an existing macro-node layer. In such aheterogeneous deployment, the low-power nodes, such as pico and femtoeNBs, may provide high end-user throughput for small areas, e.g., inindoor and hot-spot outdoor positions, while the macro layer may providefull-area coverage. Although such a heterogeneous deployment is alreadypossible under the current LTE specifications, a low-power nodedeployment in a future system may be differentiated from current systemsby at least two aspects.

First, a large number of low-power nodes in a future system may beexpected to significantly increase the end-user data rates. Thelow-power nodes may be deployed in a cluster fashion to provide highdata rates for a larger area. It may be expected that only a few UEs maybe present in each low-power cell due to the low-power cell's smallcoverage area. The traffic dynamics in the low-power cell may be large,with a relatively low average load but high instantaneous data rates.

Second, in a future system, such as that shown in FIG. 1, a UE 110 maybe expected to have dual connectivity to both a macro cell 120 and alow-power cell 130. The macro cell 120 may be served by a macro eNB 140,and the low-power cell 130 may be served by a pico or femto eNB 150.While only one low-power cell 130 is shown in the figure, a plurality oflow-power cells may be present within the coverage area of the macrocell 120.

The macro cell 120 and the low-power cell 130 may be on the samefrequency or different frequencies. The macro cell 120 may act as ananchor to provide basic radio resource control (RRC) signaling, such asmobility-related signaling and possible low-rate/high-reliability dataservices, while the low-power cell 130 may provide high-rate dataservices for traffic boosting. The current LTE systems can provide dualcell connectivity via carrier aggregation in limited deploymentscenarios, such as the macro cell 120 and the low-power cell 130 beingon different frequencies and from the same eNB. In some cases, a futuresystem may provide dual cell connectivity in additional deploymentscenarios, such the macro cell 120 and the low-power cell 130 being onthe same frequency or different frequencies as well as from the same eNBor different eNBs.

For downlink/uplink (DL/UL) transmission, the UE 110 may be informed ofthe modulation and coding scheme (MCS) of physical downlink sharedchannel/physical uplink shared channel (PDSCH/PUSCH) transmissionsthrough the five-bit MCS index in a DL/UL grant. To help the eNBdetermine which MCS to use for DL transmission, the UE feeds back thefour-bit channel quality index (CQI). The five-bit MCS index for thePDSCH/PUSCH and the four-bit CQI index are defined in 3GPP TechnicalSpecification (TS) 36.213, as shown in FIGS. 2a, 2b , and 2 c.

In LTE Rel-8, single carrier frequency division multiple access(SC-FDMA) with contiguous resource allocation was adopted for its lowpeak-to-average power ratio (PAPR) compared to orthogonal frequencydivision multiple access (OFDMA). SC-FDMA may also be referred to asdiscrete Fourier transform (DFT)-precoded orthogonal frequency divisionmultiplexing (OFDM). In Rel-10, to improve the UL throughput while stillmaintaining a reasonably low PAPR, SC-FDMA with non-contiguous resourceallocation (also referred to as clustered DFT-precoded OFDM) wasintroduced. With cluster DFT-precoded OFDM, a single DFT is applied tothe input data stream and the DFT-precoded data are mapped to up to twonon-contiguous resource block (RB) clusters. Compared to the Rel-8SC-FDMA, the flexible resource allocation in clustered DFT-precoded OFDMimproves the throughput performance. For a low-power cell in a futuresystem, spectral efficiency may be of importance, and a low PAPR may notbe a major concern due to the UE being close to the low-power cell eNBand not being power limited. Therefore, it is envisioned that a futureUE may support OFDMA in the uplink in addition to SC-FDMA.

Time division duplexing (TDD) is expected to be used more often in picocells. To better handle the high traffic dynamics in a local-areascenario where the number of UEs can be very small, dynamic TDD may beused. Each pico cell eNB may dynamically use subframes for either uplinkor downlink to match the instantaneous traffic situation in the cell.This may lead to improvements in the end-user experience as well as theoverall system throughput. However, if neighboring cells dynamicallyconfigure the UL/DL subframes independently, interference issues mayarise, as illustrated in FIG. 3. In the figure, two neighboring cells310 and 320 use different TDD UL/DL subframe configurations. If Cell 1310 is in a DL subframe while Cell 2 320 is in a UL subframe, theneNB-to-eNB interference and/or UE-to-UE interference may occur.

In eNB-to-eNB interference, during Cell 2's uplink signal reception, theCell 2 eNB 340 may see interference from the downlink transmission fromCell 1's eNB 330. This interference may degrade the UE UL throughput inCell 2 320. Furthermore, this eNB-to-eNB interference may be significantdue to the possible line-of-sight between the two eNBs 330 and 340.

In UE-to-UE interference, during UE1's downlink signal reception, UE1350 may see interference from UE2's uplink transmission. Thisinterference may degrade UE1's DL throughput. Furthermore, thisinterference may be significant if UE1 350 and UE2 360 are at cell edgeswith UE2 360 transmitting at a high power and UE1 350 seeing a weaksignal from its eNB 330.

Carrier aggregation (CA) was introduced in Rel-10. With CA, componentcarriers (CCs) in Rel-10 are backward-compatible and can be fullyaccessible to Rel-8 UEs. Each CC appears as a separate cell with its owncell ID and transmits its own primary synchronization signal/secondarysynchronization signal (PSS/SSS) and system information block (SIB)messages. Under CA, a UE can connect to one primary cell (PCell) and upto four secondary cells (SCells). The PCell is the cell that isinitially configured during connection establishment. An SCell is a cellthat may be configured after connection establishment, merely to provideadditional radio resources. A single RRC connection may be establishedwith the PCell, which controls all the CCs configured for a UE. Afterthe RRC connection is established to the PCell, reconfiguration,addition, and removal of SCells may be performed by RRC. When adding anew SCell, dedicated RRC signaling may be used to send the systeminformation (SI) of the new SCell to the UE. While in connected mode,changes of SI for an SCell may be handled by release and addition of theaffected SCell, and this may be done with a single RRC reconfigurationmessage. To reduce PAPR and save UE power, the UL control signals, suchas acknowledgements, negative acknowledgements, and channel stateinformation (ACK/NACK/CSI), may be transmitted on the PCell. The UE mayuse the same cell-specific radio network temporary identifier (C-RNTI)in the PCell and the SCell.

In addition, cross-carrier scheduling may be supported in CA forinterference coordination for the physical downlink control channel(PDCCH) in a heterogeneous network. One scheduler may be responsible forthe scheduling of all aggregated carriers. The buffer status report(BSR) and scheduling request (SR) may reflect the overall buffered datafor all carriers.

Embodiments of the present disclosure address at least four issues thatmay arise in the scenarios described above.

In a first set of embodiments, high order modulation, such as 256QAM(quadrature amplitude modulation), may be used in a pico cell to improvethe spectral efficiency.

In a second set of embodiments, OFDMA may be used in a pico cell toimprove the UL spectral efficiency.

A third set of embodiments is directed toward interference issues in adynamic TDD system. Interference coordination has previously beendiscussed for dynamic TDD systems with slow adaptation, where the rateof TDD configuration change is greater than backhaul signaling delay,e.g., 200 milliseconds (ms). In such systems, the interferencecoordination may be based on information exchanged on the X2 interfacebetween eNBs. The third set of embodiments provides interferencecoordination for a dynamic TDD network with fast adaptation, where theTDD configuration may change as fast as 10 ms. Furthermore, in a dynamicTDD network, the existing CSI feedback scheme may not be sufficient toprovide the channel conditions due to the dynamic UL/DL subframes fromthe neighboring cells. The third set of embodiments may also provideimprovement of CSI feedback for a dynamic TDD system.

In a future heterogeneous deployment, the macro layer may use frequencydivision duplexing (FDD) or TDD. The pico cell layer may be on a higherfrequency using TDD for better traffic adaptation, or the pico cell mayuse FDD. A UE may have dual connectivity to both the macro cell and thepico cell. This is the multi-serving cell scenario, which may beimplemented as carrier aggregation, with the PCell being the macroFDD/TDD and an SCell being the pico cell TDD/FDD. It is also possiblefor the PCell to be the pico cell and for the SCell to be the macrocell. The current CA in LTE assumes intra-eNB carrier aggregation andaggregated carriers having the same duplex mode, i.e., either FDD orTDD. The fourth set of embodiments provides methods to enable a UE to beserved by multiple cells, which may be from different eNBs (inter-eNBcarrier aggregation) and with different duplex modes.

Scenarios in which these embodiments may be deployed will now beconsidered. A low-power cell may be an independent cell with its owncell ID and may be on the same carrier frequency as the macro cell or adifferent carrier frequency from the macro cell. Due to the spectrumavailability at higher frequencies, such as 3.5 gigahertz (GHz), and toaid in inter-layer interference avoidance, network operators may preferto have the macro layer deployed at a lower frequency for large areacoverage and have low-power cells deployed at a higher frequency forlocal area high data rate access.

The low-power cell may use new carrier type (NCT), in either astandalone or non-standalone manner. Standalone NCT may operate on itsown and may transmit the full set of control signaling. Non-standaloneNCT means that the carrier cannot be operated on its own and thelow-power cell is to be associated with the standalone carrier of themacro cell. The UE may obtain information regarding the low-power cellnon-standalone NCT through the standalone macro carrier and in turn maybe able to access the low-power cell. Non-standalone NCT may savecontrol signals. For example, SIB messages and a cell-specific referencesignal (CRS) may not have to be transmitted, or only part of a CRS mayhave to be transmitted. However, the non-standalone NCT of the low-powercell may be expected to transmit control signals that allow the UE toidentify the cell ID, perform frequency and time tracking, and measurethe cell. The macro cell may also provide the UE certain information tohelp reduce the control signals from the non-standalone low-power cell.For example, instead of the low-power cell transmitting PSS/SSS, themacro cell may signal the UE a list of low-power cell IDs and the UE maypin down the low-power cell ID by checking the CRS sequences. In termsof better radio resource usage, non-standalone NCT may be preferred forlow-power cells. The UE may enter the network only via the macro cell ifnon-standalone NCT is deployed on the low-power cell. Standalone NCT mayor may not be backwards compatible. Backwards compatible NCT may be lessefficient as it may carry some legacy signals for legacy UEs to access.

A low-power cell may be deployed as an independent eNB with its ownbackhaul, as shown in FIG. 4a . The communication between the macro celland the low-power cell may involve the X2 interface with a backhauldelay. The low-power cell may also be deployed via a remote radio head(RRH) and may be connected to the macro cell via high-speed opticalfiber, as shown in FIG. 4b . In the case of RRH, the low-power cell andthe macro cell may belong to the same eNB and share the same backhaul.In such a case, the communication between the macro cell and thelow-power cell may be achieved with negligible delay.

The UE may have dual connectivity to the macro cell and the low-powercell during RRC_CONNECTED mode. In such a scenario, there may be atleast two use cases. In a first use case, it may be possible that themacro cell provides only basic RRC signaling, such as paging andmobility/handover (HO) related signaling, and that all the data servicesgo through the low-power cell. In a second use case, the macro cell mayprovide basic RRC signaling as well as low-rate/high-reliability dataservices, and the low-power cell may provide high-rate data services.For example, if a user is engaged in both a voice over internet protocol(VoIP) call and file downloading, then the VoIP call may go through themacro cell and the file downloading may go through the low-power cell.

Depending on the deployment scenario, the UE may have separate RRCconnections to the macro cell and to the pico cell or just one RRCconnection to the macro cell. If the macro cell and the pico cell arefrom the same eNB (e.g., the pico cell is deployed as an RRH), then oneRRC connection to the macro cell may be sufficient. If the macro celland the pico cell are from different eNBs, then two RRC connections maybe possible.

During RRC_IDLE mode, the UE may be expected to camp on the macro cellonly. Although the UE may camp on the low-power cell in the case of astandalone carrier on the low-power cell, camping on the macro cell maysimplify network operation.

The macro layer may use FDD or TDD while the low-power cell layer may beon a higher frequency using TDD for better traffic adaptation or may useFDD. The UE may have dual connectivity to both the macro cell and thepico cell. This multi-serving cell scenario may be implemented ascarrier aggregation with the PCell using macro cell FDD or TDD and theSCell using low-power cell TDD or FDD. In such cases, the UE may remainconnected to the macro cell, and the low-power cell may be added orremoved via SCell addition or removal.

It may be assumed that the UE is CA-capable and that the UE maysimultaneously communicate with the macro cell and one or more low-powercells. The macro layer and the low-power cell layer may be deployed withinter-band carrier aggregation, wherein the macro cell uses FDD and thelow-power cell uses TDD, or both the macro cell and the low-power cellmay use FDD but on different bands. In such cases, separate transceiverchains may be used. Alternatively, the macro cell and the low-power cellmay use intra-band carrier aggregation, wherein both the macro cell andthe low-power cell use FDD or TDD within the same band. In this case,for cost saving, the intra-band carrier aggregation may be implementedas a single radio frequency unit.

To save UE power, discontinuous reception (DRX) may be configured on aPCell due to the limited communication with the macro cell. Unlike thecurrent CA, in which the same DRX configuration applies to all carriers,in the embodiments disclosed herein, different DRX configurations may beapplied to a PCell and an SCell. The low-power cell may be informed ofthe subframes when the UE will communicate with the macro cell so thatthe data transmissions in the macro cell and the low-power cell may becoordinated to reliably maintain the two communication links under theUE maximum power constraint. The communication with the macro cell andthe low-power cell may occupy different subframes so that the UEcommunicates with only one cell at any given time. Alternatively, themacro cell may determine the DRX configurations for both the macro celland the pico cell.

Depending on how tightly the macro cell and the low-power cell operate,the macro cell and the low-power cell may be synchronous orasynchronous. If the macro cell and the low-power cell operate tightly,e.g., if the DRX configurations of the two cells are coordinated for UEpower saving, then the transmissions from the two cells may besynchronized. That is, the subframe boundaries may be aligned. If themacro cell and the low-power cell operate independently, then thetransmissions from the two cells may be asynchronous. Although thetransmissions from the macro cell and the low-power cell may besynchronized, the signals arriving at the UE may not be perfectlyaligned due to the different distances from the two cells to the UE.

As mentioned above, a first set of embodiments for increasing trafficcapacity in a heterogeneous deployment of low-power nodes under thecoverage of an existing macro-node layer involves supporting higherorder modulation. In a pico cell in such a heterogeneous deployment, aUE may be in close proximity to the pico cell eNB, which may providegood channel conditions. To further improve the spectral efficiency athigh signal-to-noise ratios (SNRs), higher order modulation may be usedin the pico cell. That is, the highest order of modulation that cancurrently be used in a macro cell is 64QAM. Since the channel quality ina pico cell may be expected to be good, in an embodiment, a modulationorder higher than 64QAM, such as 256QAM, may be used in a pico cell.Hereinafter, any modulation order higher than 64QAM may be referred toas 256QAM, but it should be understood that other higher modulationorders are possible. In general, any higher order modulation format thatuses more than six bits of data and can be sent over one OFDM/SC-FDMsubcarrier in a single input-single out channel may be enabled becauseof the better channel conditions expected in a low-power cellenvironment.

In an embodiment, to enable 256QAM, the existing MCS tables forPDSCH/PUSCH and the existing CQI table, shown in FIGS. 2a, 2b, and 2c ,may be modified. There may be at least three options for modifying theMCS and CQI tables. The three options may be discussed from theperspective of a pico cell transmitting to a UE, but similarconsiderations may apply to transmissions made by a UE.

A first option is to expand the MCS and CQI index tables to include256QAM. For example, the MCS index table for the PDSCH and the CQI indextable may be expanded as shown in FIGS. 5a and 5b . In these examples,the modifications relative to the prior tables are illustrated byshading. In FIG. 5a , the field modulation and coding scheme in theDL/UL grant is increased from five bits to six bits. That is, if onlyfive bits are used for the values in column 510, then only 32 values arepossible. With six bits, the expansion of the MCS table is possible.Similarly, in FIG. 5b , the CQI feedback is increased from four bits tofive bits. That is, if only four bits are used for the values in column520, then only 16 values are possible. With five bits, the expansion ofthe CQI table is possible. The existing transport block size (TBS)tables for the PDSCH and the PUSCH in 3GPP TS 36.213 may also bemodified to include the large transport block sizes for 256QAM. Anadvanced UE capable of 256QAM may assume one additional bit in the DL/ULgrant decoding and one additional bit in the CQI feedback, as well asusing the new MCS/CQI/TBS tables. The eNB may need to learn the UE'scapabilities so that the eNB can transmit the DL/UL grant in theappropriate format and assume one additional bit in CQI decoding. In anembodiment, the UE may indicate its relevant capability, i.e., whether256QAM is supported, to the eNB via RRC signaling. In anotherembodiment, certain UE categories may implicitly include such acapability, so when the UE indicates its category, its capability tosupport 256QAM is also indicated.

A second option is to redesign the MCS and CQI index tables and retainfive bits for the MCS indication and four bits for CQI feedback. In anembodiment, to cover a wider range of SNR and keep the same number ofMCS/CQI bits, the redesigned MCS/CQI index tables may have a less finegranularity of MCS/CQI. One such example is shown in FIGS. 6a and 6b .It can be seen in FIG. 6a that only eight MCS indices use a modulationorder of 2, only seven MCS indices use a modulation order of 4, and onlyten MCS indices use a modulation order of 6. This may be contrasted withFIG. 2a , where eleven MCS indices use a modulation order of 2, eightMCS indices use a modulation order of 4, and thirteen MCS indices use amodulation order of 6. It can also be seen that a modulation order of 8,which is not present in FIG. 2a , has been added to FIG. 6 a.

The existing TBS tables in 3GPP TS 36.213 may also be modified toinclude the large transport sizes for 256QAM. In such cases, an advancedUE capable of 256QAM may use the redesigned MCS/CQI/TBS tables. The eNBmay need to learn the UE's capabilities to determine whether the UE canuse the redesigned MCS/CQI tables for DL/UL grants and CQIinterpretation. In an embodiment, as with the first option, the UE mayindicate its relevant capability, i.e., whether 256QAM is supported, tothe eNB via dedicated RRC signaling. In another embodiment, certain UEcategories may implicitly include such a capability, so when the UEindicates its category, its capability to support 256QAM is alsoindicated. In either the first option or the second option, the eNB mayadditionally or alternatively query the UE's capabilities.

A third option is to design an additional set of MCS/CQI index tables tocover the high SNR region. An example of this option is shown in FIGS.7a and 7b . In this example, the UE may use the existing MCS/CQI tablesfor the low to medium SNR region and may use the new MCS/CQI tables forthe medium to high SNR region. RRC signaling may be used to indicate tothe UE which set of tables to use for MCS determination and CQIfeedback. In this option, the two sets of MCS/CQI tables may overlap(i.e., have some common entries) to ensure a smooth transition betweenthe two configurations. For example, the last nine entries of the CQItable in FIG. 2b and the first nine entries of the CQI table in FIG. 7bare the same. Again, the eNB may need to learn the UE's capabilities touse additional MCS/CQI tables for DL/UL grants and CQI interpretation.The TBS tables in 3GPP TS 36.213 may also be modified to include thelarge transport sizes for 256QAM.

As mentioned above, a second set of embodiments for increasing trafficcapacity in a heterogeneous deployment of low-power nodes under thecoverage of an existing macro-node layer involves supporting OFDMA onthe UL. In an embodiment, to support OFDMA on the UL, additional PDCCHdownlink control information (DCI) formats for UL grants may beintroduced.

In LTE Rel-10, two transmission modes were defined for the PUSCH.Transmission Mode 1 is for single antenna port transmission, whereasTransmission Mode 2 is for multiple antenna port transmission. PDCCH DCIformat 0 is used to indicate Transmission Mode 1, whereas DCI format 4is used to indicate Transmission Mode 2. In this second set ofembodiments, to support UL OFDMA transmission, new transmission modes,which may be referred to as Mode 3 and Mode 4, and new DCI formats,which may be referred to as Format 5 and Format 6, may be introduced, asshown in FIG. 8. Shading in the figure indicates the newly introducedtransmission modes and DCI formats. In this embodiment, TransmissionMode 3 and DCI Format 5 are for UEs with multiple antenna ports, whereasTransmission Mode 4 and DCI Format 6 are for UEs with a single antennaport. In some embodiments, such as when a UE is envisioned to always beequipped with multiple antennas, Transmission Mode 4 and DCI Format 6may not be included. To reduce UE complexity, the PUSCH may support upto four-layer spatial multiplexing. In some embodiments, RRC signalingmay be used to inform the UE about the transmission mode.

In an embodiment, there may be at least two options for the referencesignals for UL OFDMA transmission. In a first option, the UE may reusethe Rel-10 UL demodulation reference signal (DMRS) which is transmittedin the middle OFDM symbol of the slot (i.e., the fourth OFDM symbol ofthe slot for a normal cyclic prefix (CP) and the third OFDM symbol foran extended CP) with a Zadoff-Chu sequence in the frequency domain and apossible orthogonal cover code (OCC) in the time domain. To maintainorthogonality among the DMRSs from multiple transmission layers, CDM(code division multiplexing) may be used, and the DMRSs of differenttransmission layers may use different cyclic shifts of the sameZadoff-Chu base sequence. The same precoder for PUSCH transmission maybe applied on the DMRS. For an OFDMA transmission with non-contiguousresource allocation, similarly to the Rel-10 SC-FDMA with non-contiguousresource allocation, one Zadoff-Chu sequence may be generated with alength equal to the total number of subcarriers of the non-contiguousresource blocks.

In a second option, the UE may reuse the DL UE-specific reference signal(RS) of antenna ports 7-10. The RS for the first and second transmissionlayers and the RS for third and fourth layers may be multiplexed byfrequency division multiplexing (FDM). The RS for the first and secondlayers (or the third and fourth layers) may be multiplexed by means ofCDM by using OCC over two consecutive resource elements in the timedomain. The same precoder for PUSCH transmission may be applied on theRS. To multiplex multiple UEs on the same UL resource blocks, differentUEs may transmit on different antenna ports with orthogonal RSsequences, or different UEs may transmit on the same antenna ports withquasi-orthogonal RS sequences generated by a different scrambling seed.The second option may potentially provide better channel estimation thanthe first option due to the RS being more distributed in the RB.

In some embodiments, the new DCI Formats 5 and 6 may be based on DCIFormats 4 and 0, respectively, by replacing the resource allocationfield with the OFDMA resource allocation from DL grants. An example ofDCI Format 5 is shown in FIGS. 9a and 9b , where the modificationscompared to Format 4 are underlined. The references appearing in FIGS.9a and 9b refer to items in 3GPP TS 36.212. DCI Formats 5 and 6 canallocate more than two non-contiguous resource block (RB) clusters.

In the various embodiments under this second set of embodiments, thefollowing considerations may apply. The existing DL OFDMA resourceallocation type 2 may also be supported to allocate a set ofcontiguously allocated localized or distributed virtual resource blocks(VRBs) for UL OFDMA. In some embodiments, the Rel-10 precoding codebookfor SC-FDMA may be reused for UL OFDMA. A new codebook for UL OFDMA mayalso be designed. Due to the likely line-of-sight propagationenvironment in a pico cell, multi-layer transmission may not beefficient, and single-layer transmission with multiple antenna ports maybe preferred. In some embodiments, to reduce the payload size of theDCI, DCI Format 5 may be further simplified by, e.g., specifying onlyone transport block and one transmission layer so that the number ofbits in the field Precoding information and number of layers in DCI maybe reduced. As the channel is relatively flat in the frequency domain inpico cells and the UE connected to the pico cell may be a high data rateuser, to reduce the signal overhead, a large resource block group (RBG)size may be used to reduce the number of bits in the field Resourceblock assignment in DCI. OFDMA Transmission Mode 3 (OFDMA for multipleantenna port transmission) may fall back to either OFDMA Mode 4 (OFDMAfor single antenna port transmission) if supported or SC-FDMA Mode 1(SC-FDMA for single antenna port transmission). In an embodiment, OFDMAand SC-FDMA may be multiplexed in one UL subframe, as shown in theembodiment of FIG. 10. Instead of Transmission Mode 3 and 4 for OFDMAonly, Transmission Mode 3 and 4 may also be designed to cover bothSC-FDMA and OFDMA, with one bit in the DCI format to indicate whetherSC-FDMA or OFDMA will be used. Such an embodiment may allow the UE todynamically switch between SC-FDMA and OFDMA. Due to the smallpropagation delay spread in pico cells, smaller CP lengths may beintroduced in LTE, for example for a better spectral efficiency. Due tothe spectrum availability at high frequencies, to further enhance thedata rate in pico cells, a channel bandwidth greater than 20 megahertz(MHz) may be introduced in LTE.

A third set of embodiments is directed toward interference coordinationin a dynamic TDD network with fast adaptation, where the TDDconfiguration may change as fast as 10 ms. That is, with existingmethods for providing TDD reconfiguration information, such as sendingthe reconfiguration information in a SIB message, adaptation may occurat a rate on the order of 640 ms. In some proposed methods, adaptationmay occur at a much faster rate. A change in TDD configuration thatoccurs much slower than the backhaul signaling delay, for example slowerthan every 200 ms, may be referred to herein as slow adaptation, and achange in TDD configuration that occurs faster than the backhaulsignaling delay may be referred to herein to as fast adaptation.

In these embodiments, pico cells may schedule cell-center UEs onlyduring flexible subframes to avoid interference. That is, in one radioframe, some subframes may be static uplink or static downlink, and othersubframes may have the flexibility to be either uplink or downlink fortraffic adaptation. For example, if only UL/DL configurations 0, 1, 2,and 6 are allowed to be used in a pico cell (i.e., configurations of 5ms DL-to-UL switch-point periodicity), as shown in the example of FIG.11, the UE may assume that Subframes 0, 1, 5, and 6 are static DLsubframes including special subframes, that Subframes 2 and 7 are staticUL subframes, and that the remaining subframes are flexible subframes.Therefore, during static uplink subframes, all neighboring cells are onthe uplink, and during static downlink subframes, all neighboring cellsare on the downlink. During the flexible subframes, some cells may be onthe uplink and some cells may be on the downlink. eNB-to-eNBinterference and UE-to-UE interference may occur during the flexiblesubframes. In this third set of embodiments, cell-center UEs may bescheduled only during these flexible subframes. To improve the CSIfeedback, the third set of embodiments may also involve having the UEfeed back multiple CQIs for multiple sets of subframes to reflect thedifferent interference levels in different subframes.

In the case of TDD configurations dynamically changing as fast as 10 ms,the existing X2-based interference coordination scheme may not work dueto the delay of X2 messages. That is, the TDD configurations ofneighboring cells may not be known, as the X2-based signaling may not befast enough to update the neighboring cell information. In this case,conservative approaches to mitigate interference may be taken.

As mentioned above, in dynamic TDD, some subframes in a radio frame maybe flexible to be either uplink or downlink for traffic adaptation whileothers are static uplink or static downlink. During consecutive flexiblesubframes, to avoid an additional guard period at the UE, it may bepreferable for DL-to-UL subframe switching not to happen. It may beassumed that the radio frame boundaries of neighboring cells arealigned. The UE may be signaled about the configuration of static UL/DLand flexible subframes, or this information may be pre-configured. Eachcell may receive information to determine flexible subframes and staticsubframes in a radio frame, e.g., from operations, administration andmaintenance (OAM). The cell may be restricted to choose TDDconfigurations from a set of UL/DL configurations, e.g., TDD UL/DLconfigurations 0, 1, 2, and 6 in current LTE, which are theconfigurations with 5 ms DL-to-UL switch point periodicity.

In an embodiment, during the flexible subframes, the cell in a DLsubframe may reduce the transmit power by scheduling cell-center UEs toreduce the interference to a neighboring eNB which is in a UL subframe.Furthermore, during the flexible subframes, the cell in a UL subframemay schedule cell-center UEs so that the UEs will transmit at low powerand their UL transmissions will not create interference to the UE's DLreception in a neighboring cell which is in a DL subframe. Such anapproach virtually shrinks cell sizes in the flexible subframes to avoidinterference.

That is, an eNB may receive signal strength reports, measurementreports, power headroom reports, or other information from a pluralityof UEs and may use such information to infer the relative distances orsignal attenuation factor of the UEs from the eNB. UEs that aredetermined to be relatively closer to the eNB or have smaller signalattenuation factors than other UEs may be referred to as cell-centerUEs, and UEs that are determined to be relatively farther from the eNBor have larger signal attenuation factors than other UEs may be referredto as cell-edge UEs. It should be understood that the terms“cell-center” and cell-edge” are relative terms and that a UE referredto as a cell-center UE is not necessarily directly in the center of acell and that a UE referred to as a cell-edge UE is not necessarilydirectly at the edge of a cell. In an embodiment, the eNB uses theflexible subframes for cell-center UEs and the fixed subframes for thecell-edge as well as cell-center UEs.

Alternatively, in some embodiments, the DL transmissions in a cellscheduled in the flexible and static DL subframes obey the cell'srelative narrowband transmit power (RNTP), and the UL transmissionsscheduled in the flexible and static UL subframes obey the cell's highinterference indicator (HII). The RNTP and HII may be exchanged on X2 toinform neighboring cells. In the case of dynamic TDD with fastadaptation, as a cell may not know the TDD configurations of neighboringcells, the cell may take account of both the RNTP and the HII of aneighboring cell and attempt to schedule the transmissions such that theinterference to the neighboring cell is minimized no matter whether theneighboring cell is on a UL subframe or a DL subframe. For example, letCell 1 and Cell 2 be two neighboring cells with RNTP and HII values asshown in the example of FIG. 12. On the DL, Cell 1 assigns RBs 1-25 withRNTP=1 for high-power transmission to cell-edge UEs and assigns RBs26-50 with RNTP=0 for low-power transmission to cell-center UEs. Forinter-cell interference coordination, Cell 2 schedules its cell-edge UEson RBs 26-50. Similarly on the UL, Cell 1 assigns RBs 1-20 with HII=1for cell-edge UE transmissions and assigns RBs 21-50 with HII=0 forcell-center UE transmissions. For inter-cell interference coordination,Cell 2 schedules its cell-edge UE UL transmissions on RBs 31-50.

In one example, Cell 1 is in a DL flexible subframe. If Cell 2 is alsoin a DL flexible subframe, then Cell 1 may schedule its cell-edge UEs onRBs 1-25 and its cell-center UEs on RBs 26-50. If Cell 2 is in a ULflexible subframe, Cell 1 may still schedule its high-power cell-edgeUEs on RBs 1-25, as Cell 2 may schedule its cell-center UEs on the ULwhich are less sensitive to eNB-to-eNB interference. Meanwhile, Cell 1may schedule its cell-center UEs on RBs 26-50, as the cell-center UEsare less sensitive to UE-to-UE interference even if Cell 2 schedules itscell-edge UEs on the UL on RBs 31 to 50. Combining the above analysis,as a result, if Cell 1, which is in a DL flexible subframe, does notknow whether Cell 2 is in a UL subframe or a DL subframe, it is safe forCell 1 to schedule its cell-edge UEs on RBs 1-25 and its cell-center UEson RBs 26-50.

In another example, Cell 1 is in a UL flexible subframe. If Cell 2 isalso in a UL flexible subframe, then Cell 1 may schedule its cell-edgeUEs on RBs 1-20 and its cell-center UEs on RBs 21-50. If Cell 2 is in aDL flexible subframe, Cell 1 may still schedule its high power cell-edgeUEs on RBs 1-20, as Cell 2 may schedule its cell-center UEs on the DLwhich are less sensitive to UE-to-UE interference. Meanwhile, Cell 1 mayschedule its cell-center UEs on RBs 21-50, as the cell-center UEs areless sensitive to eNB-to-eNB interference even if Cell 2 scheduleshigh-power cell-edge UEs on the DL on RBs 26 to 50. Combining the aboveanalysis, as a result, if Cell 1, which is in a UL flexible subframe,does not know whether Cell 2 is in a UL subframe or a DL subframe, it issafe for Cell 1 to schedule its cell-edge UEs on RBs 1-20 and itscell-center UEs on RBs 21-50.

Depending on the RNTPs and HIIs of the neighboring cells, it may bepossible that the cell cannot find appropriate RBs for the cell-edgeUEs. In such a case, the cell may schedule the cell-edge UEs in thestatic DL/UL subframes and schedule only cell-center UEs in the flexibleUL/DL subframes.

In some embodiments, to minimize the eNB-to-eNB interference, in theflexible DL subframes the pico cell may avoid transmitting some of thehigh-power common control signals, such as CRS and CSI-RS. For example,such signals may be coordinated and transmitted only in the static DLsubframes. For instance, if the pico cell uses NCT, CRS may not have tobe transmitted in every DL subframe.

In some embodiments, if the common control signals, such as CRS andCSI-RS, are to be transmitted in the flexible DL subframes, the picocells may reduce their transmit power. In such cases, UEs may beconfigured to perform radio resource management (RRM) measurements andpathloss measurement based on the high-power CRS in the static DLsubframes. A new set of downlink power control parameters ρ_(A) (ratioof PDSCH energy per resource element (EPRE) to CRS EPRE for OFDM symbolsnot containing CRS), ρ_(B) (ratio of PDSCH EPRE to CRS EPRE for OFDMsymbols containing CRS), and P_(c) (ratio of PDSCH EPRE to CSI-RS EPRE)may also be defined for the flexible DL subframes and signaled to theUE. The power reduction of the CSI-RS or CRS during the flexible DLsubframes may also be signaled to the UE so that the UE can adjust theCQI estimation for the flexible DL subframes.

In some embodiments, to minimize the impact on the UE, instead of thepico cell reducing CRS/CSI-RS in the flexible DL subframes, the picocell may also let the neighboring cells know the CRS/CSI-RSconfiguration, such as the number of antenna ports, so that theneighboring eNB can perform interference cancellation.

There may be cases in which some control signals may need to betransmitted at high power during the flexible subframes. Examplesinclude the UL grant on the PDCCH or enhanced PDCCH (ePDCCH), which isused to schedule a future uplink transmission from a cell-edge UE, theDL ACK/NACK, which corresponds to the UL transmission from a cell-edgeUE a few subframes earlier, and the ACK/NACK on the PUCCH from acell-edge UE, which acknowledges the DL transmission a few subframesearlier. In some embodiments, to combat eNB-to-eNB interference,neighboring cells that are on UL subframes may use conservative MCSlevels for PUSCH transmissions. In some embodiments, to combat UE-to-UEinterference, neighboring cells that are on DL subframes may avoid DLtransmission on the band-edge RBs that are used for the PUCCH.

In some cases, one cell may be in a DL subframe while a neighboring cellmay be in a special subframe, such as Subframe 6 when Cell 1 uses a TDDconfiguration of 5 ms DL-to-UL switch-point periodicity and Cell 2 usesa TDD configuration of 10 ms DL-to-UL switch-point periodicity. In suchcases, the cell in the DL subframe may cease transmission in the lastone or two OFDM symbols so that the cell does not create interference toa neighboring cell which is in a UpPTS (Uplink Pilot Time Slot) used forthe physical random access channel (PRACH) or the sounding referencesignal (SRS). Alternatively, if only the SRS is configured in the UpPTSin the neighboring cell, then SRSs from cell-center UEs may beconfigured which are less sensitive to eNB-to-eNB interference.

With dynamic TDD configuration, the interference environment may changesignificantly from subframe to subframe. For example, in FIG. 11,Subframes 0, 1, 5, and 6 are static downlink subframes while Subframes 2and 7 are static uplink subframes. The remaining Subframes 3, 4, 8, and9 are flexible subframes which may be either DL or UL for trafficadaptation. The DL interference the UE sees during the flexiblesubframes may be different from that during the static DL subframes.This issue exists in both fast and slow adaptation of TDD configuration.

In an embodiment, to reflect the dynamic interference environment, CQIreporting may be enhanced. In some embodiments, the UE may reportmultiple CQIs for different sets of subframes, for example, per subframeCQI. Alternatively, the UE may report five CQIs in the example of FIG.11, one CQI for the static DL subframes and one CQI for each flexiblesubframe. In some embodiments, to reduce the CQI feedback overhead, twoCQIs may be fed back, one for the static DL subframes and one for theflexible subframes. The CQI for the flexible subframes may reflect anaverage of the interference levels during all of the flexible subframes.In this case, the feedback overhead reduction may be achieved at thecost of CQI accuracy.

In some embodiments, such as in the case of dynamic TDD with slowadaptation, neighboring pico cells may exchange their TDD configurationsvia X2. In an embodiment, an eNB may configure a reduced number of CQIsfor a UE with knowledge of the TDD configurations of the neighboringcells. For example, in FIG. 11, it may be assumed that a UE is in Cell 1and that Cell 2 and Cell 3 are neighboring cells. In such an example,the eNB may only configure three CQIs for the UE. The first CQI maycorrespond to the static DL subframes (Subframes 0, 1, 5, and 6). Thesecond CQI may be for Subframes 3 and 8, as the UE sees the sameinterference from Cell 2 and Cell 3 in those two subframes. The thirdCQI may be for Subframes 4 and 9, as interference from Cell 2 and Cell 3is the same in those two subframes.

In some embodiments, the resource-restricted CSI measurement introducedin Rel-10 for enhanced inter-cell interference coordination (eICIC)almost blank subframes (ABS) may be reused for the UE to report the twoCQIs corresponding to static DL subframes and flexible subframes. Themeasurement resource restriction pattern for eICIC ABS is specified inthe information elements (lEs) CQI-ReportConfig and MeasSubframePatternin 3GPP TS 36.331, as shown in FIG. 13. Due to the periodicity of ABS,the subframePatternTDD in the IE MeasSubframePattern is defined in termsof multiple radio frames. For the dynamic TDD scenario, it may besufficient to specify the measurement subframe pattern by one radioframe to reduce the signaling overhead. Therefore, in an embodiment, inthe IE MeasSubframePattern, an additional subframe pattern of 10 bitsmay be added, which is indicated by underlining in the example of FIG.13.

If more than two CQIs are desired for dynamic TDD to reflect theinterference level in an individual flexible subframe, then moremeasurement subframe subsets may be defined in the IE CQI-ReportConfig,an example of which is shown in FIG. 14, with the additional measurementsubframe subsets indicated by underlining.

A fourth set of embodiments will now be considered. In the multi-servingcell scenario, a UE may be connected to both a macro cell and a picocell, and the macro cell and the pico cell may be from the same ordifferent eNBs. The macro cell and the pico cell may be on the samefrequency or different frequencies. The fourth set of embodimentsinvolves supporting inter-eNB carrier aggregation in the multi-servingcell scenario. The macro cell may be the PCell and the pico cell may bethe SCell. In the case of the macro cell and the pico cell beingco-channel, PCell and SCell refer to cells on the same frequency. In thecurrent LTE CA, PCell and SCell are on different frequencies. The fourthset of embodiments may further involve having a UE feed picocell-related L1 control signals, such as ACK/NACK/CSI/SR, back to thepico cell. The fourth set of embodiments may also involve having thepico cell signal the macro cell about dynamic TDD with fast adaptation.

In future systems, it may be envisioned that the macro layer may use FDDor TDD while the pico cell layer may use TDD or FDD. In some such cases,the macro cell may operate on a lower carrier frequency relative to thepico cell due to the propagation characteristics. For better usage ofthe available bandwidth and for traffic flow adaptation, TDD may be usedat the pico cell. Alternatively, the pico cell may operate in FDD with asmall bandwidth. For example, as depicted in the example of FIG. 15, themacro cell may operate over {f_(D1),f_(U1)}±Δf_(m)/2 in FDD, and thepico cell may operate in TDD over {f_(c2)}±Δf_(s)/2, where f_(D1),f_(U1) and Δf_(m) are the downlink carrier frequency, the uplink carrierfrequency, and the bandwidth, respectively, used by the macro cell, andf_(c2) and Δf_(s) are the carrier frequency and the channel bandwidthused by the pico cell using TDD. f_(c2) may preferably be higher thanf_(D1) and f_(U1). Alternatively, as illustrated in the example of FIG.16, the pico cell may operate in FDD over {f_(D2),f_(U2)}±Δf_(s)/2,where f_(D2), f_(U2) and Δf_(s) are the downlink carrier frequency, theuplink carrier frequency, and the channel bandwidth, respectively, usedby the pico cell. The LTE FDD carrier frequencies may be selected fromany of the evolved universal terrestrial radio access (E-UTRA) operatingbands 1-14 or 17-28 as defined in Table 5.5-1 in 3GPP TS 36.101, whereasE-UTRA operating bands 33-44 may be selected for the pico cell's TDDoperation. In some cases, the UE may have dual connectivity to the macrocell and the pico cell. In such cases, the multi-serving cell scenariomay be implemented as carrier aggregation with the PCell using macro FDDand one or more SCells using pico cell TDD/FDD.

If the pico cells on a higher frequency are deployed via RRHs, then themulti-serving cell scenario may be considered an intra-eNB carrieraggregation with multiple timing advances (TAs), except that theaggregated carriers may be of different duplex modes FDD and TDD. The CAscheme currently being discussed in 3GPP Rel-11 assumes that theaggregated carriers are of the same duplex mode, either FDD or TDD. Ifthe existing CA design is reused, the pico cell and the macro cell mayoperate tightly. However, if the macro cell and the pico cell are tooperate more independently, at least seven new design aspects may beintroduced in various embodiments. These new design aspects may alsoapplicable to the case of the pico cell and the macro cell beingdeployed as independent eNBs.

First, due to the good channel conditions in the pico cell, in someembodiments, cross-carrier scheduling may be disabled, and the UL/DLgrants for the data transmissions on the pico cell and the macro cellmay come from the respective cells. Alternatively, the UL/DL grants ofboth the macro cell and the pico cell may be transmitted on the picocell. That is, the UL/DL grants for both the PCell and the SCell maycome from the SCell. In the current LTE CA, the UL/DL grants for thePCell can only come from PCell. In the pico cell environment, since PAPRand UE power may not be major concerns, the UL PUCCH control signals,such as the ACK/NACK/CSI corresponding to the pico cell, may betransmitted to the pico cell, i.e., the SCell. To enable this, a bit maybe added in the RRCConnectonReconfiguration message so that when anSCell is added, the UE knows that the UL control signal corresponding tothe SCell will be transmitted back to the SCell. This is illustrated inFIGS. 17a and 17b , with the disclosed modifications represented byunderlining. Alternatively, the UL control signals (e.g., ACK/NACK/CSI)of both the macro cell and the pico cell may go to the pico cell to saveUE power.

Second, in some embodiments, a macro PCell and a pico cell SCell mayhave separate schedulers, as shown in the examples of FIG. 18 and FIG.19. Information, such as the subframes when the UE will communicate withthe macro cell, may be exchanged between the macro cell and the picocell so that the two schedulers may coordinate the data transmissions.

Third, in some embodiments, if the UE separates the traffic for a macroPCell and a pico cell SCell, the UE may report separate BSRs/SRs toreflect the buffered data corresponding to the pico cell and the macrocell. The BSRs/SRs may be sent to the corresponding macro cell and picocell. The BSRs/SRs may also be sent together to the macro cell or to thepico cell.

Fourth, in some embodiments, such as in the case of dynamic TDD withfast adaptation on the pico cell, a bit may be added in the IERadioResourceConfigCommonSCell so that the UE knows that dynamic TDDwith fast adaptation is used in the pico cell. This is illustrated inFIG. 20, with the disclosed modifications represented by underlining.The UE knows that, for the added SCell, the UE may ignore the TDD UL/DLconfiguration specified in tdd-Config-r10 and, instead, usepre-configured information to assume certain subframes as static DL/ULsubframes and the remaining subframes as flexible subframes. Forexample, if only UL/DL configurations 0, 1, 2, and 6 are allowed in anSCell (i.e., configurations of 5 ms DL-to-UL switch-point periodicity),the UE may assume that Subframes 0, 1, 5, and 6 are static DL subframesincluding special subframes, that Subframes 2 and 7 are static ULsubframes, and that the remaining subframes are flexible subframes. Thestatic UL/DL subframes may be pre-configured or signaled to the UE.

Fifth, in some embodiments, a UE may have different C-RNTIs in a PCelland an SCell. For example, to facilitate the macro cell in assigning apico C-RNTI to the UE when adding one or more pico cells as SCells, eachpico cell may reserve some C-RNTIs for UEs that can have dualconnectivity with macro cells and pico cells. The pico cell may notifythe macro cell about the reserved C-RNTIs. When the macro cell adds thepico cell as an SCell for a UE, the macro cell may pick a pico cellC-RNTI from the reserved pool and assign the pico cell C-RNTI to the UE.Alternatively, instead of the pico cell reserving C-RNTIs, the macrocell may signal the pico cell to ask for a C-RNTI whenever the macrocell desires a pico cell C-RNTI.

Sixth, in some embodiments, the pico cell may send its systeminformation, e.g., the TDD configuration, to the macro eNB. When themacro eNB adds the pico cell as an SCell, the macro eNB may deliver thesystem information of the pico cell to the UE. If dynamic TDDconfiguration with slow adaptation is used in the pico cell, the picocell may notify the macro cell about the actual TDD configuration. Ifdynamic TDD configuration with fast adaptation is used in the pico cell,the pico cell may notify the macro cell that dynamic TDD with fastadaptation is used in the pico cell. If the static UL/DL subframes arenot pre-configured, the pico cell may notify the macro cell about thestatic UL/DL subframes.

Seventh, in some embodiments, the macro PCell uses FDD and the picoSCell uses TDD. If ACK/NACKs of both the PCell and the SCell need to besent to the macro PCell, to support ACK/NACK of aggregated FDD and TDD,PUCCH Format 3, which can carry up to 20 bits of ACK/NACK, may be usedto deliver the ACK/NACK bits from both FDD and TDD carriers. In theworst case of TDD configuration 5, in which Subframe 2 needs to feedback ACK/NACK of PDSCH transmissions in nine DL subframes, combiningwith the ACK/NACK of the FDD carrier, the 20 bits may be sufficient aseach PDSCH transmission supports at most two codewords. In the case ofthe macro PCell using TDD and the pico SCell using FDD, if ACK/NACKs ofboth the PCell and the SCell need to be sent to the macro PCell, theACK/NACKs on the SCell may be multiplexed or bundled over multiplesubframes and/or codewords and sent on the PCell's TDD UL subframe.

If the pico cell is deployed as an independent eNB with its ownbackhaul, then the inter-eNB carrier aggregation may be different fromthe current CA, which assumes intra-eNB carrier aggregation. Adifference from the above RRH case is that any communication between themacro cell and the pico cell may involve X2 messages and backhaul delay.At least five aspects related to such scenarios may be disclosed.

First, due to the large delay on X2, the macro cell and the pico cellmay operate more independently than the case of a pico cell beingdeployed via RRH. Therefore, in some embodiments, cross-carrierscheduling may not be used. The UL control signals of the pico cell,such as the ACK/NACK/CSI corresponding to the transmissions in the picocell, may go to the pico cell, and a bit in theRRCConnectonReconfiguration message may be used to enable this, as shownin FIGS. 17a and 17 b.

Second, in some cases, such as in the case of an independent pico celleNB, the macro cell and the pico cell may each have their ownschedulers, as shown in the examples of FIG. 18 and FIG. 19. In anembodiment, information, such as the subframes when the UE willcommunicate with the macro cell, may be exchanged between the macro celland the pico cell via X2 so that the two schedulers may coordinate thedata transmissions to reliably maintain the two communication linksunder the UE maximum power constraint. In some embodiments, the UE mayreport separate BSRs/SRs to reflect the buffered data on the pico celland the macro cell.

Third, in some embodiments, such as in the case of dynamic TDD with fastadaptation in the pico cell, a bit may be added in the IERadioResourceConfigCommonSCell to notify the UE that dynamic TDD withfast adaptation is used in the pico cell. This is shown in FIG. 20. Thestatic UL/DL subframes may be either pre-configured or signaled to theUE.

Fourth, in some embodiments, different C-RNTIs may be used in a macroPCell and a pico cell SCell. Similarly to the RRH case, this may beachieved by, for example, the pico cell reserving some C-RNTIs for themacro cell to use. Alternatively, the macro cell may explicitly ask thepico cell for a C-RNTI via X2 when desired.

Fifth, in some embodiments, the pico cell may send its systeminformation, e.g., the TDD configuration, to the macro eNB via X2. Whenthe macro eNB adds the pico cell as an SCell, the eNB may deliver thesystem information of the pico cell to the UE. If dynamic TDDconfiguration with slow adaptation is used in the pico cell, the picocell may notify the macro cell about the actual TDD configuration viaX2. If dynamic TDD configuration with fast adaptation is used in thepico cell, the pico cell may notify the macro cell via X2 that dynamicTDD with fast adaptation is used in the pico cell. If the static UL/DLsubframes are not pre-configured, the pico cell may notify the macro eNBabout the static UL/DL subframes via X2.

In an embodiment, if simultaneous UE transmissions to the macro cell andthe pico cell exceed the UE maximum power, the UE may scale down thetransmit power to the pico cell first and prioritize the transmission tothe macro cell. Alternatively, to avoid exceeding the UE maximum power,the network may avoid simultaneous transmission to the macro cell andthe pico cell by letting the UE transmit all data to the pico cell. Forexample, in the case of a macro cell and a pico cell deployed asintra-eNB CA and the macro cell and the pico cell operating tightly(e.g., one scheduler for both), the network may route the macro celldata to the pico cell by scheduling the UE to send all data on theSCell.

In an example scenario, the secondary component carriers at a pico cellmay be deployed as non-standalone carriers. That is, UEs may not beconnected to the LTE network through the pico cell. Instead, a UE mayinitially connect to the LTE evolved packet core (EPC) via the macrocell and may subsequently switch to the pico cell. The aggregated systeminformation may be broadcast by the macro cell. The pico cell may informthe macro cell of the relevant system information, such as the TDDconfiguration. In the event of updated system information, the pico cellor the macro cell may page the UEs connected to the pico cell, and/orthe differential system information may be sent to those UEs indedicated RRC signaling by the pico cell. To reduce the systeminformation overhead, the SIBs containing the pico cell SI may betransmitted less frequently. In an embodiment, a new SIB message mayinclude this information. In some embodiments, the existing schemes inCA may be used to handle the SIB changes of the pico cell. For example,the SCell may first be released and then the same SCell may be added,and this may be done with a single RRC reconfiguration message. Sincethe network entry operation is through the macro cell, this change maynot affect the network entry time. Some of the RRC functionality of thepico cell, preferably those functions which are not delay sensitive, maybe performed at the macro cell. For example, HO decision making may bedone at the macro cell.

The above may be implemented by a network element. A simplified networkelement is shown with regard to FIG. 21. In the figure, network element3110 includes a processor 3120 and a communications subsystem 3130,where the processor 3120 and communications subsystem 3130 cooperate toperform the methods described above.

Further, the above may be implemented by a UE. One exemplary device isdescribed below with regard to FIG. 22. UE 3200 is typically a two-waywireless communication device having voice and data communicationcapabilities. UE 3200 generally has the capability to communicate withother computer systems on the Internet. Depending on the exactfunctionality provided, the UE may be referred to as a data messagingdevice, a two-way pager, a wireless e-mail device, a cellular telephonewith data messaging capabilities, a wireless Internet appliance, awireless device, a mobile device, or a data communication device, asexamples.

Where UE 3200 is enabled for two-way communication, it may incorporate acommunication subsystem 3211, including a receiver 3212 and atransmitter 3214, as well as associated components such as one or moreantenna elements 3216 and 3218, local oscillators (LOs) 3213, and aprocessing module such as a digital signal processor (DSP) 3220. As willbe apparent to those skilled in the field of communications, theparticular design of the communication subsystem 3211 will be dependentupon the communication network in which the device is intended tooperate.

Network access requirements will also vary depending upon the type ofnetwork 3219. In some networks network access is associated with asubscriber or user of UE 3200. A UE may require a removable useridentity module (RUIM) or a subscriber identity module (SIM) card inorder to operate on a network. The SIM/RUIM interface 3244 is normallysimilar to a card-slot into which a SIM/RUIM card can be inserted andejected. The SIM/RUIM card can have memory and hold many keyconfigurations 3251, and other information 3253 such as identification,and subscriber related information.

When required network registration or activation procedures have beencompleted, UE 3200 may send and receive communication signals over thenetwork 3219. As illustrated in the figure, network 3219 can consist ofmultiple base stations communicating with the UE.

Signals received by antenna 3216 through communication network 3219 areinput to receiver 3212, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection and the like. Analog to digital (A/D) conversion of a receivedsignal allows more complex communication functions such as demodulationand decoding to be performed in the DSP 3220. In a similar manner,signals to be transmitted are processed, including modulation andencoding for example, by DSP 3220 and input to transmitter 3214 fordigital to analog (D/A) conversion, frequency up conversion, filtering,amplification and transmission over the communication network 3219 viaantenna 3218. DSP 3220 not only processes communication signals, butalso provides for receiver and transmitter control. For example, thegains applied to communication signals in receiver 3212 and transmitter3214 may be adaptively controlled through automatic gain controlalgorithms implemented in DSP 3220.

UE 3200 generally includes a processor 3238 which controls the overalloperation of the device. Communication functions, including data andvoice communications, are performed through communication subsystem3211. Processor 3238 also interacts with further device subsystems suchas the display 3222, flash memory 3224, random access memory (RAM) 3226,auxiliary input/output (I/O) subsystems 3228, serial port 3230, one ormore keyboards or keypads 3232, speaker 3234, microphone 3236, othercommunication subsystem 3240 such as a short-range communicationssubsystem and any other device subsystems generally designated as 3242.Serial port 3230 could include a USB port or other port known to thosein the art.

Some of the subsystems shown in the figure perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 3232 and display3222, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the processor 3238 may be stored in apersistent store such as flash memory 3224, which may instead be aread-only memory (ROM) or similar storage element (not shown). Thoseskilled in the art will appreciate that the operating system, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile memory such as RAM 3226. Received communication signals mayalso be stored in RAM 3226.

As shown, flash memory 3224 can be segregated into different areas forboth computer programs 3258 and program data storage 3250, 3252, 3254and 3256. These different storage types indicate that each program canallocate a portion of flash memory 3224 for their own data storagerequirements. Processor 3238, in addition to its operating systemfunctions, may enable execution of software applications on the UE. Apredetermined set of applications that control basic operations,including at least data and voice communication applications forexample, will normally be installed on UE 3200 during manufacturing.Other applications could be installed subsequently or dynamically.

Applications and software may be stored on any computer readable storagemedium. The computer readable storage medium may be a tangible or intransitory/non-transitory medium such as optical (e.g., CD, DVD, etc.),magnetic (e.g., tape) or other memory known in the art.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. Naturally,one or more memory stores may be available on the UE to facilitatestorage of PIM data items. Such PIM application may have the ability tosend and receive data items, via the wireless network 3219. Furtherapplications may also be loaded onto the UE 3200 through the network3219, an auxiliary I/O subsystem 3228, serial port 3230, short-rangecommunications subsystem 3240 or any other suitable subsystem 3242, andinstalled by a user in the RAM 3226 or a non-volatile store (not shown)for execution by the processor 3238. Such flexibility in applicationinstallation increases the functionality of the device and may provideenhanced on-device functions, communication-related functions, or both.For example, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing the UE 3200.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem3211 and input to the processor 3238, which may further process thereceived signal for output to the display 3222, or alternatively to anauxiliary I/O device 3228.

A user of UE 3200 may also compose data items such as email messages forexample, using the keyboard 3232, which may be a complete alphanumerickeyboard or telephone-type keypad, among others, in conjunction with thedisplay 3222 and possibly an auxiliary I/O device 3228. Such composeditems may then be transmitted over a communication network through thecommunication subsystem 3211.

For voice communications, overall operation of UE 3200 is similar,except that received signals may typically be output to a speaker 3234and signals for transmission may be generated by a microphone 3236.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on UE 3200. Although voiceor audio signal output is preferably accomplished primarily through thespeaker 3234, display 3222 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call related information for example.

Serial port 3230 may normally be implemented in a personal digitalassistant (PDA)-type UE for which synchronization with a user's desktopcomputer (not shown) may be desirable, but is an optional devicecomponent. Such a port 3230 may enable a user to set preferences throughan external device or software application and may extend thecapabilities of UE 3200 by providing for information or softwaredownloads to UE 3200 other than through a wireless communicationnetwork. The alternate download path may for example be used to load anencryption key onto the device through a direct and thus reliable andtrusted connection to thereby enable secure device communication. Aswill be appreciated by those skilled in the art, serial port 3230 canfurther be used to connect the UE to a computer to act as a modem.

Other communications subsystems 3240, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between UE 3200 and different systems ordevices, which need not necessarily be similar devices. For example, thesubsystem 3240 may include an infrared device and associated circuitsand components or a Bluetooth™ communication module to provide forcommunication with similarly enabled systems and devices. Subsystem 3240may further include non-cellular communications such as WiFi or WiMAX.

The UE and other components described above might include a processingcomponent that is capable of executing instructions related to theactions described above. FIG. 23 illustrates an example of a system 3300that includes a processing component 3310 suitable for implementing oneor more embodiments disclosed herein. In addition to the processor 3310(which may be referred to as a central processor unit or CPU), thesystem 3300 might include network connectivity devices 3320, randomaccess memory (RAM) 3330, read only memory (ROM) 3340, secondary storage3350, and input/output (I/O) devices 3360. These components mightcommunicate with one another via a bus 3370. In some cases, some ofthese components may not be present or may be combined in variouscombinations with one another or with other components not shown. Thesecomponents might be located in a single physical entity or in more thanone physical entity. Any actions described herein as being taken by theprocessor 3310 might be taken by the processor 3310 alone or by theprocessor 3310 in conjunction with one or more components shown or notshown in the drawing, such as a digital signal processor (DSP) 3380.Although the DSP 3380 is shown as a separate component, the DSP 3380might be incorporated into the processor 3310.

The processor 3310 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 3320,RAM 3330, ROM 3340, or secondary storage 3350 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 3310 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 3310 may beimplemented as one or more CPU chips.

The network connectivity devices 3320 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, universal mobile telecommunications system (UMTS) radiotransceiver devices, long term evolution (LTE) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 3320 may enable the processor 3310 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 3310 might receiveinformation or to which the processor 3310 might output information. Thenetwork connectivity devices 3320 might also include one or moretransceiver components 3325 capable of transmitting and/or receivingdata wirelessly.

The RAM 3330 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 3310. The ROM 3340 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 3350. ROM 3340 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 3330 and ROM 3340 istypically faster than to secondary storage 3350. The secondary storage3350 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 3330 is not large enough to hold all workingdata. Secondary storage 3350 may be used to store programs that areloaded into RAM 3330 when such programs are selected for execution.

The I/O devices 3360 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 3325 might be considered to be a component of the I/Odevices 3360 instead of or in addition to being a component of thenetwork connectivity devices 3320.

In an embodiment, a UE is provided. The UE comprises a processorconfigured such that the UE receives or transmits a modulated signalthat has a modulation order higher than 64QAM and feeds back a CQI thatcorresponds to the modulation order higher than 64QAM. The modulationorder may be 256QAM. The signal transmission may be based on a table ofMCS indices that contains more than 32 MCS indices and may be based on atable of CQI feedback indices that contains more than 16 CQI indices. Atleast six bits may be used to encode each of the MCS indices in aresource assignment grant and at least five bits may be used to encodeeach of the CQI indices in a CQI report. The signal transmission may bebased on a table of MCS indices that contains 32 MCS indices and may bebased on a table of CQI feedback indices that contains 16 CQI indices. Amodulation order of 8 may be included in the table of MCS indices andthe table of CQI indices and may be associated with MCS indices and CQIindices that are not associated with a modulation order of 2, 4, or 6.The signal transmission may be based on at least two tables of MCSindices and may be based on at least two tables of CQI feedback indices.Each table of MCS indices may contain 32 MCS indices and each table ofCQI feedback indices may contain 16 CQI indices. The UE may use a firsttable of MCS indices and a first table of CQI feedback indices when aSNR associated with the signal transmission is determined to have arelatively low to medium value and the UE may use a second table of MCSindices and a second table of CQI feedback indices when the SNR isdetermined to have a relatively medium to high value. At least one entryin the first table of CQI feedback indices may be the same as at leastone entry in the second table of CQI feedback indices, and at least oneentry in the first table of MCS indices may be the same as at least oneentry in the second table of MCS indices. The UE may receive informationindicating which table of MCS indices and which table of CQI feedbackindices to use. The UE may transmit information indicating that the UEis capable receiving or transmitting signals that have an MCS that has amodulation order higher than 64QAM. The UE may transmit the informationresponsive to receiving a request from a network element for anindication of the UE's capabilities. The UE may belong to a category ofUEs, and members of the category may be implicitly indicated as havingthe capability to receive or transmit signals transmitted with an MCSthat has a modulation order higher than 64QAM.

In another embodiment, a method is provided for communication in awireless telecommunication network. The method comprises receiving ortransmitting, by a UE, a modulated signal that has a modulation orderhigher than 64QAM and feeding back, by the UE, a CQI that corresponds tothe modulation order higher than 64QAM. The modulation order may be256QAM. The signal transmission may be based on a table of MCS indicesthat contains more than 32 MCS indices and may be based on a table ofCQI feedback indices that contains more than 16 CQI indices. At leastsix bits may be used to encode each of the MCS indices in a resourceassignment grant and at least five bits may be used to encode each ofthe CQI indices in a CQI report. The signal transmission may be based ona table of MCS indices that contains 32 MCS indices and may be based ona table of CQI feedback indices that contains 16 CQI indices. Amodulation order of 8 may be included in the table of MCS indices andthe table of CQI indices and may be associated with MCS indices and CQIindices that are not associated with a modulation order of 2, 4, or 6.The signal transmission may be based on at least two tables of MCSindices and may be based on at least two tables of CQI feedback indices.Each table of MCS indices may contain 32 MCS indices and each table ofCQI feedback indices may contain 16 CQI indices. The UE may use a firsttable of MCS indices and a first table of CQI feedback indices when aSNR associated with the signal transmission is determined to have arelatively low to medium value and the UE may use a second table of MCSindices and a second table of CQI feedback indices when the SNR isdetermined to have a relatively medium to high value. At least one entryin the first table of CQI feedback indices may be the same as at leastone entry in the second table of CQI feedback indices, and at least oneentry in the first table of MCS indices may be the same as at least oneentry in the second table of MCS indices. The UE may receive informationindicating which table of MCS indices and which table of CQI feedbackindices to use. The UE may transmit information indicating that the UEis capable receiving or transmitting signals that have an MCS that has amodulation order higher than 64QAM. The UE may transmit the informationresponsive to receiving a request from a network element for anindication of the UE's capabilities. The UE may belong to a category ofUEs, and members of the category may be implicitly indicated as havingthe capability to receive or transmit signals transmitted with an MCSthat has a modulation order higher than 64QAM.

In another embodiment, a network element is provided. The networkelement comprises a processor configured such that the network elementreceives or transmits a modulated signal that has a modulation orderhigher than 64QAM and receives a CQI that corresponds to the modulationorder higher than 64QAM. The modulation order may be 256QAM. The signaltransmission may be based on a table of MCS indices that contains morethan 32 MCS indices and may be based on a table of CQI feedback indicesthat contains more than 16 CQI indices. At least six bits may be used toencode each of the MCS indices in a resource assignment grant and atleast five bits may be used to encode each of the CQI indices in a CQIreport. The signal transmission may be based on a table of MCS indicesthat contains 32 MCS indices and may be based on a table of CQI feedbackindices that contains 16 CQI indices. A modulation order of 8 may beincluded in the table of MCS indices and the table of CQI indices andmay be associated with MCS indices and CQI indices that are notassociated with a modulation order of 2, 4, or 6. The signaltransmission may be based on at least two tables of MCS indices and maybe based on at least two tables of CQI feedback indices. Each table ofMCS indices may contain 32 MCS indices and each table of CQI feedbackindices may contain 16 CQI indices. A first table of MCS indices and afirst table of CQI feedback indices may be used when a SNR associatedwith the signal transmission is determined to have a relatively low tomedium value and a second table of MCS indices and a second table of CQIfeedback indices may be used when the SNR is determined to have arelatively medium to high value. At least one entry in the first tableof CQI feedback indices may be the same as at least one entry in thesecond table of CQI feedback indices, and at least one entry in thefirst table of MCS indices may be the same as at least one entry in thesecond table of MCS indices. The network element may transmit to a UEinformation indicating which table of MCS indices and which table of CQIfeedback indices the UE is to use. The network element may request froma UE an indication of the UE's capabilities regarding modulation orderswith which the UE is capable of receiving or transmitting signals.

In another embodiment, a UE is provided. The UE comprises a processorconfigured such that the UE transmits a PUSCH that uses OFDMA, whereinthe PUSCH transmission occurs with a first transmission mode when the UEtransmits on a plurality of antenna ports and with a second transmissionmode when the UE transmits on a single antenna port, and wherein thePUSCH transmission occurs responsive to the UE receiving an uplink grantthat uses one of a first DCI format associated with the firsttransmission mode or a second DCI format associated with the secondtransmission mode. A reference signal used for the PUSCH transmissionmay be at least one of: a DMRS for PUSCH in 3GPP LTE releases prior toRelease 12; and a UE-specific RS for antenna ports 7-10 in 3GPP LTEreleases prior to Release 12. A precoder used for the PUSCH transmissionmay be applied on the reference signal. When the reference signal is theDMRS, code division multiplexing may be used to maintain orthogonalityamong a plurality of DMRSs from a plurality of transmission layers andDMRSs of different transmission layers may use different cyclic shifts.When the reference signal is the UE-specific RS for antenna ports 7-10,a first reference signal for one of a first transmission layer and asecond transmission layer and a second reference signal for one of athird transmission layer and a fourth transmission layer may bemultiplexed by frequency division multiplexing. When the referencesignal is the UE-specific RS for antenna ports 7-10, a first referencesignal for a first transmission layer and a second reference signal fora second transmission layer may be multiplexed by code divisionmultiplexing. When the reference signal is the UE-specific RS forantenna ports 7-10, the UE and another UE may transmit on differentantenna ports with orthogonal reference signal sequences. When thereference signal is the UE-specific RS for antenna ports 7-10, the UEand another UE may transmit on the same antenna port withquasi-orthogonal reference signal sequences generated by differentscrambling seeds. Only one transport block and only one transmissionlayer may be specified in the first DCI format to reduce payload size ofthe DCI. More than two non-contiguous RB clusters may be specified inone of the first DCI format or the second DCI format. A RBG size largerthan the RBG size in 3GPP LTE releases prior to Release 12 may be usedin one of the first DCI format or the second DCI format. An OFDMAtransmission and a SC-FDMA transmission may be multiplexed in an uplinksubframe. An OFDMA transmission and a SC-FDMA transmission may be usedin different uplink subframes. The first transmission mode and thesecond transmission mode may allow both OFDMA transmission and SC-FDMAtransmission, and a bit in one of the first DCI format or the second DCIformat may indicate whether OFDMA transmission or SC-FDMA transmissionis to be used.

In another embodiment, a method is provided for communication in awireless telecommunication network. The method comprises transmitting,by a UE, a PUSCH that uses OFDMA, wherein the PUSCH transmission occurswith a first transmission mode when the UE transmits on a plurality ofantenna ports and with a second transmission mode when the UE transmitson a single antenna port, and wherein the PUSCH transmission occursresponsive to the UE receiving an uplink grant that uses one of a firstDCI format associated with the first transmission mode or a second DCIformat associated with the second transmission mode. A reference signalused for the PUSCH transmission may be at least one of: a DMRS for PUSCHin 3GPP LTE releases prior to Release 12; and a UE-specific RS forantenna ports 7-10 in 3GPP LTE releases prior to Release 12. A precoderused for the PUSCH transmission may be applied on the reference signal.When the reference signal is the DMRS, code division multiplexing may beused to maintain orthogonality among a plurality of DMRSs from aplurality of transmission layers and DMRSs of different transmissionlayers may use different cyclic shifts. When the reference signal is theUE-specific RS for antenna ports 7-10, a first reference signal for oneof a first transmission layer and a second transmission layer and asecond reference signal for one of a third transmission layer and afourth transmission layer may be multiplexed by frequency divisionmultiplexing. When the reference signal is the UE-specific RS forantenna ports 7-10, a first reference signal for a first transmissionlayer and a second reference signal for a second transmission layer maybe multiplexed by code division multiplexing. When the reference signalis the UE-specific RS for antenna ports 7-10, the UE and another UE maytransmit on different antenna ports with orthogonal reference signalsequences. When the reference signal is the UE-specific RS for antennaports 7-10, the UE and another UE may transmit on the same antenna portwith quasi-orthogonal reference signal sequences generated by differentscrambling seeds. Only one transport block and only one transmissionlayer may be specified in the first DCI format to reduce payload size ofthe DCI. More than two non-contiguous RB clusters may be specified inone of the first DCI format or the second DCI format. A RBG size largerthan the RBG size in 3GPP LTE releases prior to Release 12 may be usedin one of the first DCI format or the second DCI format. An OFDMAtransmission and a SC-FDMA transmission may be multiplexed in an uplinksubframe. An OFDMA transmission and a SC-FDMA transmission may be usedin different uplink subframes. The first transmission mode and thesecond transmission mode may allow both OFDMA transmission and SC-FDMAtransmission, and a bit in one of the first DCI format or the second DCIformat may indicate whether OFDMA transmission or SC-FDMA transmissionis to be used.

In another embodiment, a method is provided for communication in awireless telecommunication network. The method comprises providing, by anetwork element, to a UE, an uplink grant that uses one of a first DCIformat associated with a first transmission mode or a second DCI formatassociated with a second transmission mode; and receiving, by thenetwork element, from the UE, responsive to the UE receiving the uplinkgrant, a PUSCH that uses OFDMA, wherein the PUSCH transmission occurswith the first transmission mode when the UE transmits on a plurality ofantenna ports and with the second transmission mode when the UEtransmits on a single antenna port. The first transmission mode and thesecond transmission mode may allow both OFDMA transmission and SC-FDMAtransmission, and the network element may include a bit in one of thefirst DCI format or the second DCI format to indicate whether OFDMAtransmission or SC-FDMA transmission is to be used.

In another embodiment, a network element in a first cell in a wirelesstelecommunication network is provided. The network element comprises aprocessor configured such that the network element provides uplink anddownlink grants in the first cell, wherein the first cell is a low-powercell within the coverage area of a second, high-power cell, and whereinthe first cell acts as a secondary cell and the second cell acts as aprimary cell in a carrier aggregation mode, and wherein at least oneuplink control signal is received by one of only the first cell or boththe first cell and the second cell.

In another embodiment, a method is provided for communication in awireless telecommunication network. The method comprises providing, by anetwork element in a first cell in the network, uplink and downlinkgrants in the first cell, wherein the first cell is a low-power cellwithin the coverage area of a second, high-power cell, and wherein thefirst cell acts as a secondary cell and the second cell acts as aprimary cell in a carrier aggregation mode, and wherein at least oneuplink control signal is received by one of only the first cell or boththe first cell and the second cell.

In another embodiment, a UE configured to maintain dual connectivitywith a first cell and a second cell in a wireless telecommunicationnetwork is provided. The UE comprises a processor configured such thatthe UE sends at least one uplink control signal to one of only the firstcell or both the first cell and the second cell, wherein the second cellis a high-power cell and the first cell is a low-power cell within thecoverage area of the second cell, and wherein the second cell acts as aprimary cell and the first cell acts as a secondary cell in a carrieraggregation mode.

The following are incorporated herein by reference for all purposes:3GPP Technical Specification (TS) 36.101, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.300, and 3GPP TS 36.331.

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the scopeof the present disclosure. The present examples are to be considered asillustrative and not restrictive, and the intention is not to be limitedto the details given herein. For example, the various elements orcomponents may be combined or integrated in another system or certainfeatures may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A network element in a first cell in a wirelesstelecommunication network, the network element comprising: at least onestorage device; and a processor configured to execute instructionsstored on the at least one storage device such that when executed, thenetwork element provides uplink and downlink grants in the first cell,wherein the first cell is a low-power cell within the coverage area of asecond, high-power cell, and wherein the first cell acts as a secondarycell and the second cell acts as a primary cell in a carrier aggregation(CA) mode, wherein the network element schedules the uplink and downlinkgrants based on information received from the second cell via an X2interface between the first and second cells, and wherein at least oneuplink control signal is received by one of only the first cell or boththe first cell and the second cell, wherein the processor is furtherconfigured to execute the instructions such that when the networkelement schedules a user equipment (UE) to avoid exceeding the UE'smaximum power, the UE sends all of its data to the first cell, whereinthe UE is scheduled to avoid exceeding the UE's maximum power viasignaling from the network element.
 2. The network element of claim 1,wherein the uplink and downlink grants are for data transmissions onboth the first cell and the second cell, and wherein differentdiscontinuous reception (DRX) configurations are applied on the firstcell and the second cell in the CA mode.
 3. The network element of claim1, wherein the network element receives at least one of a buffer requestor a scheduling request independently from a buffer request or ascheduling request sent to the second cell.
 4. The network element ofclaim 1, wherein the network element uses a different duplex mode in thefirst cell than that used in the second cell during the CA mode, whereindynamic time division duplexing (TDD) with fast adaptation is thedifferent duplex mode used in the first cell, and wherein theRadioResourceConfigCommonSCell information element in Third GenerationPartnership Project (3GPP) Technical Specification (TS) 36.331 ismodified to indicate to a user equipment (UE) that dynamic TDD with fastadaptation is in use in the first cell.
 5. The network element of claim1, wherein the network element assigns a first cell radio networktemporary identifier (C-RNTI) to a user equipment (UE), and wherein thefirst C-RNTI is different from a second C-RNTI that the second cellassigns to the UE, and wherein the network element indicates to the UEto use a higher modulation order in the first cell than in the secondcell.
 6. The network element of claim 5, wherein the network elementindicates to the UE to use the higher modulation order such that the UEmodulates data in the first cell using an order of modulation greaterthan 64QAM (quadrature amplitude modulation) and modulates data in thesecond cell using an order of modulation equal to or less than 64QAM. 7.The network element of claim 1, wherein the network element in the firstcell reserves at least one C-RNTI for the second cell to assign to atleast one UE configured to maintain dual connectivity with the firstcell and the second cell, and wherein the network element notifies thesecond cell about the at least one reserved C-RNTI.
 8. The networkelement of claim 1, wherein the network element receives all datatransmitted from a UE from which the at least one uplink control signalis received, the at least one uplink control signal comprising at leastone acknowledgement (ACK) signal, negative acknowledgement (NACK) signalor channel state information (CSI) signal.
 9. The network element ofclaim 1, wherein the network element uses a different duplex mode in thefirst cell than that used in the second cell during the CA mode, whereina time division duplexing (TDD) mode is the different duplex mode usedin the first cell while a frequency division duplexing (FDD) mode isused in the second cell during the CA mode, and wherein the first celloperates on a higher frequency than the second cell.
 10. A method forcommunication in a wireless telecommunication network, the methodcomprising: providing, by a network element in a first cell in thenetwork, uplink and downlink grants in the first cell, wherein the firstcell is a low-power cell within the coverage area of a second,high-power cell, and wherein the first cell acts as a secondary cell andthe second cell acts as a primary cell in a carrier aggregation (CA)mode, wherein the network element schedules the uplink and downlinkgrants based on information received from the second cell via an X2interface between the first and second cells, and wherein at least oneuplink control signal is received by one of only the first cell or boththe first cell and the second cell; and when the network elementschedules a user equipment (UE) to avoid exceeding the UE's maximumpower, scheduling, by the network element, the UE to send all of itsdata to the first cell, wherein the UE is scheduled to avoid exceedingthe UE's maximum power via signaling from the network element.
 11. Themethod of claim 10, wherein the uplink and downlink grants are for datatransmissions on both the first cell and the second cell, and whereindifferent discontinuous reception (DRX) configurations are applied onthe first cell and the second cell in the CA mode.
 12. The method ofclaim 10, wherein the network element receives at least one of a bufferrequest or a scheduling request independently from a buffer request or ascheduling request sent to the second cell.
 13. The method of claim 10,further comprising using, by the network element, a different duplexmode in the first cell than that used in the second cell during the CAmode, wherein dynamic time division duplexing (TDD) with fast adaptationis the different duplex mode used in the first cell, and wherein theRadioResourceConfigCommonSCell information element in Third GenerationPartnership Project (3GPP) Technical Specification (TS) 36.331 ismodified to indicate to a user equipment (UE) in the first cell thatdynamic TDD with fast adaptation is in use in the first cell.
 14. Themethod of claim 10, wherein the network element assigns a first cellradio network temporary identifier (C-RNTI) to a user equipment (UE),and wherein the first C-RNTI is different from a second C-RNTI that thesecond cell assigns to the UE, and wherein the network element indicatesto the UE to use a higher modulation order in the first cell than in thesecond cell.
 15. The method of claim 10, wherein the network elementreserves at least one C-RNTI for the second cell to assign to at leastone UE configured to maintain dual connectivity with the first cell andthe second cell, and wherein the network element notifies the secondcell about the at least one reserved C-RNTI.
 16. The method of claim 10,wherein the network element receives all data transmitted from a UE fromwhich the at least one uplink control signal is received, the at leastone uplink control signal comprising at least one acknowledgement (ACK)signal, negative acknowledgement (NACK) signal or channel stateinformation (CSI) signal.
 17. The method of claim 10, further comprisingusing, by the network element, a different duplex mode in the first cellthan that used in the second cell during the CA mode, wherein a timedivision duplexing (TDD) mode is the different duplex mode used in thefirst cell while a frequency division duplexing (FDD) mode is used inthe second cell during the CA mode, and wherein the first cell operateson a higher frequency than the second cell.
 18. A user equipment (UE)configured to maintain dual connectivity with a first cell and a secondcell in a wireless telecommunication network, the UE comprising: atleast one storage device; and a processor configured to executeinstructions stored on the at least one storage device such that whenexecuted, the UE sends at least one uplink control signal to one of onlythe first cell or both the first cell and the second cell, wherein thesecond cell is a high-power cell and the first cell is a low-power cellwithin the coverage area of the second cell, and wherein the second cellacts as a primary cell and the first cell acts as a secondary cell in acarrier aggregation mode, the processor further configured to executethe instructions such that when the UE is scheduled to avoid exceedingthe UE's maximum power, the UE sends all of its data to the first cell,wherein the UE is scheduled to avoid exceeding the UE's maximum powervia signaling from a scheduler in the wireless telecommunicationnetwork.
 19. The UE of claim 18, wherein the UE sends one of a bufferstatus report or a scheduling request to the first cell independentlyfrom a buffer status report or a scheduling request the UE sends to thesecond cell.
 20. The UE of claim 18, wherein the UE is assigned a firstcell radio network temporary identifier (C-RNTI) by the first cell, andwherein the first C-RNTI is different from a second C-RNTI that isassigned to the UE by the second cell.
 21. The UE of claim 18, theprocessor further configured to execute the instructions such that whenexecuted during the carrier aggregation mode, the UE is scheduled by thescheduler to send uplink control signals to the SCell rather than thePCell, the uplink control signals comprising at least one of anacknowledgement (ACK), negative acknowledgement (NACK), or channel stateinformation (CSI).